It has been found that bark and small limbs can be conveniently removed from logs by passing the log between a pair of upper and lower rotating drums that carry chain flails. The chain beats against the log to tear off small limbs and bark.
In order to take off the bark and limbs from all the way around the log, the chain flails on the upper drum must reach down along the sides of the log to at least the mid-point. Conversely, the chain flails on the lower drum must reach upwardly along the sides of the log to the mid-point.
The logs are conveyed lengthwise through the apparatus with the bottom of the logs at an established feed line. The lower drum is mounted below this feed line and the length of the lower drum chain flails is dictated by the diameter of the largest diameter logs to be fed through the apparatus. The upper drum is mounted, not just above the feed line, but above the feed line by an amount that will accommodate the largest diameter log. The length of the upper drum chain flails must reach down, not just to the mid-point of the largest diameter log, but down to the mid-point of the smallest diameter log supported at the feed line (and obviously at a lower point than the larger diameter log).
It will be appreciated that in apparatus prior to the present invention, the lower drum flail length may be required to be twenty inches long with six inches of the length between the drum and the feed line, and the remaining fourteen inches (the flailing portion) accommodating logs, e.g. from a four inch diameter to a twenty-eight inch diameter. The upper flail length however has to be extended an additional twelve inches to thirty-two inches in order to reach downwardly to the mid-point of the four inch log.
The additional twelve inches of length required for the upper flails adds height to the apparatus dimensions and creates design difficulties particularly for portable debarking apparatus. A shorter length flail is desirable for other reasons as well.